The present invention refers to an electrical heating device, in particular, for fluids such as liquid fuel, with a heating element which comprises an electrical resistance and which can be connected to an electrical power source.
One such device is known in the market. In it, a so called “heating cartridge” is arranged in a fuel line, such as an oil supply line for an oil burner. The cartridge comprises a heating coil which has a thermo-element and extends into the fuel stream that is transported inside the fuel line. The thermo-element is used to record and regulate the temperature. If an electrical voltage is applied to the heating cartridge, it and the fuel running past will expand. The advantage of such a heating process is that the heated fuel has a low viscosity and therefore forms a very thin fuel film on the wall of the customary hollow-cone nozzle. This in turn reduces the flow even when the nozzle opening is relatively wide. A relatively wide nozzle opening is desirable to prevent plugging.
In this manner, low performance atomizing burners can be used with a relatively wide nozzle diameter. Furthermore, due to the low viscosity, the nozzle atomizes the fuel more evenly and into a finer spray, thus improving ignition. The overall effect of heating the fuel is a reduction in fuel consumption.
However, the device known in the market has the disadvantage that its design is complicated, and it is therefore difficult to integrate it into the oil supply line. Furthermore, regulating with a thermo-element and an electronic regulator and control unit is relatively complex, which increases the cost. Finally, in many cases, the heating coil for heating the fuel has to become quite hot, which causes the fuel that is in direct contact with the heating coil to evaporate and to form an insulating vapor lock between the remaining liquid fuel and the heating coil. This thermally insulating vapor lock reduces the heat transfer between the heating coil and the fuel, which means that more energy is required for heating the fuel, and the fuel is not evenly heated.
Another electrical heating device of the above named type that is known in the market is used, for example, as a hot plate. In this device, too, the temperature of the hot plate is recorded by a thermo-element and adjusted via a separate regulator and control unit. This is also technically complex and, in addition, the reaction is sluggish.
It is therefore the object of the present invention to further develop a heating device of the above named type such that it is easy to manufacture and easy to integrate, that its technical complexity is reduced, that the fuel can be heated evenly, and that a quick reaction time can be achieved for temperature regulation.